A heat exchanger utilizing one fluid to cool one or more separate fluids finds common usage as a radiator for the coolant system of an internal combustion engine in automotive vehicles. A down-flow radiator of conventional design has a radiator core extending between upper and lower tanks or headers with the cooled fluid leaving the lower tank to a water pump which forces the fluid through the engine block. The hot fluid is returned to the upper tank of the radiator where it passes through a plurality of finned tubes forming the core with a second fluid (air) being drawn through the core and around the tubes and fins to cool the fluid forming the coolant.
Also requiring cooling in a vehicle is the transmission oil for the vehicle transmission or the engine oil. A water-to-oil heat exchanger of an elongated tubular design is conventionally positioned within the lower tank and has fittings extending to the exterior of the lower tank to connect to conduits extending from the transmission housing. One form of water-to-oil cooler utilizes a tubular conduit having an annular envelope for circulation of the oil with the cooled fluid circulating around and centrally through the envelope to provide a large heat transfer area.
A cross-flow radiator is formed with vertically oriented tanks and a tube and fin radiator core for horizontal flow or with a plurality of horizontally extending plates in a vertical stack and corrugated fins located in the spacing between the plates, such as shown in U.S. Pat. No. 3,207,216. However, in the arrangement shown in the above patent, the positioning of a water-to-oil cooler in the outlet header presents a problem in view of the space requirements and need for exterior fittings. All of the above down-flow and cross-flow radiator constructions involve a substantial number of parts and utilize two separate units to cool both the engine coolant and the transmission oil. The present invention provides a single heat exchanger construction to function to cool both the engine coolant and transmission and/or engine oil.